<template>
  <ul class="mo-paging">
    <!-- prev -->
    <li :class="['paging-item', 'paging-item--prev', {'paging-item--disabled': index === 1}]" @click="prev">prev</li>
    <!-- first -->
    <!-- <li :class="['paging-item', 'paging-item--first', {'paging-item--disabled' : index === 1}]" @click="first">first</li> -->
    <li :class="['paging-item', 'paging-item--more']" v-if="showPrevMore">...</li>
    <li :class="['paging-item', {'paging-item--current': index === pager}]" v-for="pager in pagers" @click="go(pager)">{{ pager }}</li>
    <li :class="['paging-item', 'paging-item--more']" v-if="showNextMore">...</li>
    <!-- last -->
    <!-- <li :class="['paging-item', 'paging-item--last', {'paging-item--disabled' : index === pages}]" @click="last">last</li> -->
    <!-- next -->
    <li :class="['paging-item', 'paging-item--next', {'paging-item--disabled': index === pages}]" @click="next">next</li>
  </ul>
</template>
<script type="text/ecmascript-6">
export default {
  name: 'MoPaging',
  // 通过props来接受从父组件传递过来的值
  props: {
    // 页面中的可见页码，其他的以...替代, 必须是奇数
    perPages: {
      type: Number,
      default: 5
    },
    // 当前页码
    pageIndex: {
      type: Number,
      default: 1
    },
    // 每页显示条数
    pageSize: {
      type: Number,
      default: 10
    },
    // 总记录数
    total: {
      type: Number,
      default: 0
    }
  },
  methods: {
    prev () {
      if (this.index > 1) {
        this.go(this.index - 1)
      }
    },
    next () {
      if (this.index < this.pages) {
        this.go(this.index + 1)
      }
    },
    first () {
      if (this.index !== 1) {
        this.go(1)
      }
    },
    last () {
      if (this.index !== this.pages) {
        this.go(this.pages)
      }
    },
    go (page) {
      if (this.index !== page) {
        this.index = page
        // 父组件通过change方法来接受当前的页码
        this.$emit('change', this.index)
      }
    }
  },
  computed: {
    // 计算总页码
    pages () {
      return Math.ceil(this.size / this.limit)
    },
    // 计算页码，当count等变化时自动计算
    pagers () {
      const array = []
      const perPages = this.perPages
      const pageCount = this.pages
      let current = this.index
      const _offset = (perPages - 1) / 2
      const offset = {
        start: current - _offset,
        end: current + _offset
      }
      // -1, 3
      if (offset.start < 1) {
        offset.end = offset.end + (1 - offset.start)
        offset.start = 1
      }
      if (offset.end > pageCount) {
        offset.start = offset.start - (offset.end - pageCount)
        offset.end = pageCount
      }
      if (offset.start < 1) offset.start = 1
      this.showPrevMore = (offset.start > 1)
      this.showNextMore = (offset.end < pageCount)
      for (let i = offset.start; i <= offset.end; i++) {
        array.push(i)
      }
      return array
    }
  },
  data () {
    return {
      index: this.pageIndex, // 当前页码
      limit: this.pageSize, // 每页显示条数
      size: this.total || 1, // 总记录数
      showPrevMore: false,
      showNextMore: false
    }
  },
  watch: {
    pageIndex(val) {
      this.index = val || 1
    },
    pageSize(val) {
      this.limit = val || 10
    },
    total(val) {
      this.size = val || 1
    }
  }
}
</script>

<style scoped lang="stylus" rle="stylesheet/stylus">
@import "~common/stylus/variable"
.mo-paging {
    display: inline-block;
    padding: 0;
    margin: 1rem 0;
    font-size: 0;
    list-style: none;
    user-select: none;
    > .paging-item {
        display: inline;
        font-size: 14px;
        position: relative;
        padding: 6px 12px;
        line-height: 1.42857143;
        text-decoration: none;
        // border: 0px solid #ccc;
        background-color: #fff;
        margin-left: -1px;
        cursor: pointer;
        color: $title-color;
        &:first-child {
            margin-left: 0;
        }
        &:hover {
            background-color: #f0f0f0;
            color: $color-icon-mini
        }
        &.paging-item--disabled,
        &.paging-item--more{
            background-color: #fff;
            color: #505050;
        }
        // 禁用
        &.paging-item--disabled {
            cursor: not-allowed;
            opacity: .75;
        }
        &.paging-item--more,
        &.paging-item--current {
            cursor: default;
        }
        // 选中
        &.paging-item--current {
            color: $color-icon-mini
            position: relative
            z-index: 1
        }
    }
}
</style>
